CONSTANCY OF MAGNECIIYSTALLIC FORCE IN DIFFERING MEDIA. 
163 
directions in a crystal of bismuth, is not altered by great changes in the magnetic 
character of the medium surrounding it; since they remain the same in phosphorus, 
alcohol, water, carbonic acid gas, air, and solution of protosulphate of iron a list 
which includes both diamagnetic and paramagnetic substances. 
3377. Tourmaline . — As a paramagnecrystal, and therefore in contrast with bismuth, 
a black tourmaline was selected, regular in form, and nearly 0’37 of an inch in 
diameter. A piece, 0-36 in length, was cut off with flat ends; its weight was 40*4 
grains, and its specific gravity 3*076. When suspended between the flat-faced poles 
with the axis of the prism horizontal, that axis set strongly in the equatorial direction, 
by virtue of the differential magnecrystallic force. On using a silk suspension (3369.) 
the necessary upsetting torsion force was as follows : — 
Temp. Torsion force. 
In air 57° ... 2534 
In alcohol * . . 56 ... 2546 
In water 56 ... 2541 
In solution of sulphate of iron saturated ... 57 ... 2632 
3378. These results sufficiently indicate that the torsion force, and therefore the 
differential magnecrystallic force, was alike for the same temperature, whatever the 
character of the surrounding medium. But to give more certainty, the fine silver 
torsion wire (3369.) was employed, and with the following results : — 
Water . . . . 
Olive oil 
Alcohol 
Air 
Saturated solution of protosuljihate of iron 
Temp. 
Torsion for 
65° 
. . . 1082 
. 65 
. . . 1085 
. 65 
. . . 1081 
. 65 
. . . 1079 
. 65 
. . . 1081 
which sufficiently prove that the magnecrystallic force remained the same in degree, 
notwithstanding great variations in the character of the surrounding media. The 
angle between the upsetting points was 90° ; but it has not been abstracted from the 
experimental results, inasmuch as that correction would make no difference in their 
character. 
3379. The native 'protocarhonate of iron is very magnecrystallic, being also as a 
whole highly paramagnetic. A rhomboid was selected, and, being placed with its 
greatest length vertical and its shortest axis horizontal, was reduced, by grinding at 
the sides, to a rough octagonal prism, having an upright length of 0*6 of an inch, and 
an average horizontal breadth of 0*37 ; — the weight was 47*5 grains ant! the magne- 
crystallic axis horizontal. The magnetic force of this cr3^stal was so great, that 
though the fine silver torsion wire (3369.) was employed with it, the pole-pieces had 
to be opened to the full extent of the magnet, i. e, to 4*7 inches, before the torsion 
force was sufficiently reduced to render the set of the crj^stal manageable. To lessen 
the power of the magnet by a cross bar of iron at the sides, I considered objection- 
